Improvement of electrical and mechanical properties of laser welded lap joints via dimensional optimization

Abstract

With the proliferation of electric drivetrains, the development and optimization of joining techniques for the fabrication of battery packs became a prime manufacturing topic. Decreasing the electrical resistance and increasing the mechanical strength of the welds at the individual cell level are of great importance not only for productivity and efficiency but also for safety and sustainability purposes. Lasers offer an advanced, highly automatable solution for battery cell joining. Usually, the optimization focuses on the laser parameters or the scanning speed. However, the most widespread battery welding geometry, the so-called lap geometry, allows alternative possibilities for joint property optimization. The novelty of our approach is that we focus on systematic experimental investigation of the effects of dimensional parameters and the layout of the weld pattern. Systematic experiments reveal that the shape and size of the weld area have substantial effect on the properties of the laser welded joint. Our results prove that a rather substantial gain can be achieved in both the electrical and mechanical properties when the weld consists of at least two parallel bead segments. We also show that it is beneficial by both means if the segments have the greatest individual length and placed apart at the maximum feasible distance. The orientation of the straight segments affects the mechanical and electrical behavior differently: strongest welds consist of weld segments oriented in parallel, while the smallest resistance can be achieved using segments oriented perpendicular to the direction of current flow, respectively.